Evidence of Twisted flux-tube Emergence in Active Regions

Elongated magnetic polarities are observed during the emergence phase of bipolar active regions (ARs). These extended features, called magnetic tongues, are interpreted as a consequence of the azimuthal component of the magnetic flux in the toroidal flux-tubes that form ARs. We develop a new systematic and user-independent method to identify AR tongues. Our method is based on determining and analyzing the evolution of the AR main polarity inversion line (PIL). The effect of the tongues is quantified by measuring the acute angle [ tau] between the orientation of the PIL and the direction orthogonal to the AR main bipolar axis. We apply a simple model to simulate the emergence of a bipolar AR. This model lets us interpret the effect of magnetic tongues on parameters that characterize ARs ( e.g. the PIL inclination and the tilt angles, and their evolution). In this idealized kinematic emergence model, tau is a monotonically increasing function of the twist and has the same sign as the magnetic helicity. We systematically apply our procedure to a set of bipolar ARs that were observed emerging in line-of-sight magnetograms over eight years. For most of the cases studied, the tongues only have a small influence on the AR tilt angle since tongues have a much lower magnetic flux than the more concentrated main polarities. From the observed evolution of tau, corrected for the temporal evolution of the tilt angle and its final value when the AR is fully emerged, we estimate the average number of turns in the subphotospherically emerging flux-rope. These values for the 41 observed ARs are below unity, except for one. This indicates that subphotospheric flux-ropes typically have a low amount of twist, i.e. highly twisted flux-tubes are rare. Our results demonstrate that the evolution of the PIL is a robust indicator of the presence of tongues and constrains the amount of twist in emerging flux-tube

Stochastic Resonance: influence of a f−κf^{-\kappa} noise spectrum

Here, in order to study \textit{stochastic resonance} (SR) in a double-well potential when the noise source has a spectral density of the form $f^{-\kappa}$ with varying $\kappa$, we have extended a procedure, introduced by Kaulakys et al (Phys. Rev. E \textbf{70}, 020101 (2004)). In order to have an analytical understanding of the results, we have obtained an effective Markovian approximation, that allows us to make a systematic study of the effect of such kind of noises on the SR phenomenon. The comparison of numerical and analytical results shows an excellent qualitative agreement indicating that the effective Markovian approximation is able to correctly describe the general trends.Comment: 11 pages, 6 figures, submitted to Euro.Phys.J.

User requirements for multimedia indexing and retrieval of unedited audio-visual footage - RUSHES

Multimedia analysis and reuse of raw un-edited audio visual content known as rushes is gaining acceptance by a large number of research labs and companies. A set of research projects are considering multimedia indexing, annotation, search and retrieval in the context of European funded research, but only the FP6 project RUSHES is focusing on automatic semantic annotation, indexing and retrieval of raw and un-edited audio-visual content. Even professional content creators and providers as well as home-users are dealing with this type of content and therefore novel technologies for semantic search and retrieval are required. As a first result of this project, the user requirements and possible user-scenarios are presented in this paper. These results lay down the foundation for the research and development of a multimedia search engine particularly dedicated to the specific needs of the users and the content

Photovoltaic System Adoption in Water Related Technologies – A Review

Water and energy are intimately related, as water is required for energy applications and energy is required for water-based technologies. Two large groups of photovoltaic adoptions have been identified in this review: first, those in which the photovoltaic system is separated from the water technology. In second group, the photovoltaic system is in physical contact with the water technology thereby its performance is affected either in a positive or negative way. The novelty of this review work lies in the classification of photovoltaic system adoption in various water related technologies. Apart from classification, discussions on system configurations, working aspects, performance aspects, economic aspects and scope for further investigations have been presented in detail. Wastewater treatment plants are identified to be the most suitable site for photovoltaic module installation and utilization. Among power sectors, hydro power plants are highly compatible with photovoltaic adoption because it enhances hydro power plant’s operation time and utilization. Floating photovoltaic, submerged photovoltaic, agrivoltaic, aquavoltaic and solar photovoltaic + water disinfection are relatively new, highly attractive and have more scope for further improvements. Agrivoltaic and aquavoltaic increases crop & sea food production, enhances farmers’ income, encourage clean energy transition and rural electrification. Research works in the area of unmanned photovoltaic based water vehicles, photovoltaic salt harvest and various applications of water based photovoltaic/thermal modules have also been discussed. This review will serve as a guidebook for researchers and policy makers to identify and select suitable configuration of photovoltaic–water related technologies for implementation and further investigations

Stationary distributions of sums of marginally chaotic variables as renormalization group fixed points

We determine the limit distributions of sums of deterministic chaotic variables in unimodal maps assisted by a novel renormalization group (RG) framework associated to the operation of increment of summands and rescaling. In this framework the difference in control parameter from its value at the transition to chaos is the only relevant variable, the trivial fixed point is the Gaussian distribution and a nontrivial fixed point is a multifractal distribution with features similar to those of the Feigenbaum attractor. The crossover between the two fixed points is discussed and the flow toward the trivial fixed point is seen to consist of a sequence of chaotic band mergers.Comment: 7 pages, 2 figures, to appear in Journal of Physics: Conf.Series (IOP, 2010

Pencil-Beam Surveys for Trans-Neptunian Objects: Limits on Distant Populations

Two populations of minor bodies in the outer Solar System remain particularly elusive: Scattered Disk objects and Sedna-like objects. These populations are important dynamical tracers, and understanding the details of their spatial- and size-distributions will enhance our understanding of the formation and on-going evolution of the Solar System. By using newly-derived limits on the maximum heliocentric distances that recent pencil-beam surveys for Trans-Neptunian Objects were sensitive to, we determine new upper limits on the total numbers of distant SDOs and Sedna-like objects. While generally consistent with populations estimated from wide-area surveys, we show that for magnitude-distribution slopes of {\alpha} > 0.7-1.0, these pencil-beam surveys provide stronger upper limits than current estimates in literature.Comment: Submitted to Icaru